Taking a feat in Dungeons & Dragons often seems risky because they become available at the same time as ability score increases. Since ability scores play such an important role in everything from how swiftly a character moves to how much damage they can deal out or take, players often forgo feats in favor of maxing out their Dexterity, Wisdom and Constitution scores.
However, since Monks already have solid action economy, taking time to analyze feats that will enhance their already outstanding abilities without detracting from their routine is essential. Monks can quickly become one of the most dependable members of the party, and taking extra steps to ensure that they remain standing can go a long way.
Crusher Help a Monk Protect Their Party
Regardless of the Monk's subclass, moving enemies away from allies, or even themselves, can be a literal life saver in complicated combat situations. Crusher allows the player to push the target five feet into an unoccupied space after landing a successful hit that deals bludgeoning damage -- perfect for Monks and their fists. Crusher also allows the player to increase their Constitution (or Strength, though that's not really necessary for Monks) by +1, which means it's not a total stat score sacrifice.
This feat also provides an opportunity to gain advantage on attack rolls made against the creature until the start of the player's next turn after a critical hit dealt by bludgeoning damage. That means allies have a higher change to connect their hits against that enemy, possibly even wiping it off the map before the Monk's next turn.
Mobile Makes a Fast Character Even Faster
First and foremost, Mobile increases the player's movement by 10 feet, which means the incredibly agile and speedy Monk can get to where they need to be even faster. Making melee attacks against an enemy also negates their ability to make an attack of opportunity for the rest of the turn, even if the attack doesn't land. That means the Monk can pop in, throw a few staggering punches and walk away without having to worry about the target getting their revenge right away.
Using the Dash action through difficult terrain also frees up the Monk's movement. That means they can walk through obstacles without losing their full movement and speed, potentially catching up to a fleeing enemy before they escape.
Alert Monks Can Move First - Or Close to It
Alert is a helpful way to make sure the Monk can move first (or least relatively early on) during combat. It grants an additional +5 to their initiative which, coupled with a high DEX modifier, provides a maximum of +10 to initiative rolls. This means that even a natural one will come an initiative of 11, which really isn't bad. The Alert Monk also can't be surprised as long as they are conscious.
To make that lack of surprise even more valuable, enemies aren't able to gain advantage on their attack rolls when the Monk can't see them. A feat like that is really going to annoy Roguish enemies in a big way because they will struggle to get that precious Sneak Attack damage they often rely on.
Additional Options for Monks
Sentinel is another useful feat for Monks, as it drops an enemy's speed to zero if they are hit with an opportunity attack. Holding them in place makes it impossible for them to get away, increasing the likelihood of allies reaching the target to do damage of their own. Creatures also provoke opportunity attacks from the Sentinel, even if they use the disengage action.
Squat Nimbleness allows a Monk to boost their DEX (or STR) by +1. They also increase their walking speed by +5, which, when coupled with a feat like Mobile, could give the Monk even more opportunities to get in front of enemies trying to make a run for it. They also gain advantage on Strength or Dexterity checks to avoid be grappled.
Finally, Second Chance increases DEX, CON or Charisma by +1 and allows the player to force an enemy to reroll an attack once per short or long rest.